409
FXUS65 KBYZ 201930
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
130 PM MDT SAT JUN 20 2026
KEY MESSAGES
- UNSETTLED CONDITIONS THROUGH MONDAY. HIGHEST CHANCES FOR
SIGNIFICANT PRECIPITATION (HALF AN INCH OR MORE) WILL BE EAST
OF A FORSYTH TO SHERIDAN, WY LINE.
- GUSTY WINDS, SMALL HAIL, AND HEAVY DOWNPOURS ARE POSSIBLE WITH
ANY THUNDERSTORMS THROUGH TONIGHT.
- SEASONAL WEATHER CONDITIONS, WITH LOW CHANCES (10-30%) FOR
AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS, EXPECTED FOR
THE REST OF THE WORK WEEK. TEMPERATURES APPROACHING 90 DEGREES
BY FRIDAY.
- STRONG STORM SYSTEM TAKING SHAPE FOR NEXT WEEKEND. STAY TUNED.
DISCUSSION
THIS AFTERNOON THROUGH SATURDAY...
UPPER LEVEL DISTURBANCE MOVING THIS DIRECTION OUT OF IDAHO HAS
SPREAD A GOOD DEAL OF PACIFIC MOISTURE OVER THE REGION THIS
AFTERNOON. RADAR IS SHOWING LIGHT RETURNS ACROSS THE REGION AT
NOON, THOUGH MUCH OF THIS ACTIVITY IS NOT REACHING THE GROUND JUST
YET. THERE IS A CLUSTER OF THUNDERSTORMS DEVELOPING SOUTH FO CODY,
WY THAT IS FORECAST TO MOVE NORTHEAST AND EXPAND IN COVERAGE AS IT
MOVES INTO THE BIGHORN MOUNTAINS BY 5PM OR SO. ANOTHER AREA OF
THUNDERSTORMS IS TAKING SHAPE OVER SW MONTANA AND WILL LIKEWISE
EXPAND AS IT MOVES INTO THE WESTERN MOUNTAINS LATER THIS
AFTERNOON. AS THIS ACTIVITY SPURRED BY MID LEVEL ENERGY AND
MOISTURE MOVES THIS DIRECTION, LOW LEVEL SOUTHEASTERLY WINDS ARE
ADVECTING IN PLAINS MOISTURE. SURFACE DEW POINTS HAVE RISEN INTO
THE MID 40S TO LOWER 50S EAST OF A HYSHAM TO SHERIDAN WY LINE
HELPING TO BOOST THE PRECIPITABLE WATER VALUES OVER 0.9IN IN THIS
AREA. ADDITIONAL MOISTURE ADVECTION IS EXPECTED THIS AFTERNOON AND
EVENING RESULTING IN PWATS INCREASING WELL ABOVE AN INCH OVER THIS
SAME REGION, WHICH WILL BE THE FUEL FOR HEAVIER SHOWERS AND
THUNDERSTORMS THROUGH LATE TONIGHT.
FURTHER WEST MOISTURE ADVECTION WILL CONTINUE WITH EASTERLY WINDS
WORKING TO FILL IN TO THE FOOTHILLS. THE POTENTIAL FOR LOCALLY
HEAVY DOWNPOURS EXISTS FOR THESE WESTERN AREAS ESPECIALLY WHERE
UPSLOPE WINDS INTERSECT THE FOOTHILLS, BUT OVERALL COVERAGE OF
STRONGER STORMS WILL BE LESS THAN AREAS FURTHER EAST WHERE OVERALL
MOISTURE LEVELS ARE HIGHER. STORM MOTIONS WILL BE RELATIVELY SLOW
AT AROUND 15MPH ACROSS THE AREA. THIS WILL ALSO SUPPORT THE
POTENTIAL FOR THE LOCALLY HEAVY DOWNPOURS AS STORMS WILL LINGER
LONGER OVER A PARTICULAR AREA. A QUICK HALF AN INCH OR MORE OF
PRECIPITATION IS POSSIBLE WITH THE HEAVIER SHOWERS AND
THUNDERSTORMS.
THE LATEST SPC CONVECTIVE OUTLOOK AND HI-RES MODEL GUIDANCE
CONTINUES TO KEEP JUST A MARGINAL RISK (5% CHANCE) FOR A SEVERE
THUNDERSTORM RIGHT ALONG THE MT/WY LINE, WITH STRONG WIND GUSTS
THE MAIN THREAT. ONGOING CLOUD COVER AND LIGHT SHOWERS HAVE
SUPPRESSED WARMING SO FAR TODAY WITH MESO- ANALYSIS SHOWING ML-
CAPE VALUES UNDER 100 J/KG EARLY THIS AFTERNOON. GIVEN THE
ADDITIONAL CLOUD COVER ANTICIPATED TO ADVECT THIS WAY BY UPSTREAM
CONVECTION AND THE APPROACHING UPPER DISTURBANCE ITS GOING TO BE
TOUGH TO GET ENOUGH HEATING TO BOOST THOSE CAPE VALUES ENOUGH TO
SUPPORT SEVERE STORM DEVELOPMENT. MOST STORMS THROUGH TONIGHT WILL
BE SUB-SEVERE WITH WIND GUSTS IN THE 40 TO 50 MPH RANGE THE MAIN
THREAT, BUT CAN'T RULE OUT SMALL HAIL GIVEN RELATIVELY LOW
FREEZING LEVELS AROUND 8KFT AGL.
EXPECT SHOWERS AND THUNDERSTORM ACTIVITY TO CONTINUE THROUGH THE
NIGHT WITH THE HIGHEST CHANCES RESIDING EAST OF BILLINGS. UPPER
DISTURBANCE SLOWLY WORKS THROUGH THE REGION THROUGH TOMORROW
MORNING. PRECIPITATION CHANCES WILL GENERALLY DECREASE OVER THE
WESTERN HALF OF THE AREA BY LATE MORNING AS DRIER AIR WORKS IN
BEHIND THE TROF PASSAGE, BUT THERE WILL BE AFTERNOON INSTABILITY
SHOWERS DURING THE AFTERNOON MAINLY OVER MOUNTAIN AND FOOTHILLS
LOCATIONS. BY EARLY EVENING PRECIPITATION CHANCES OVER THE EAST
WILL QUICKLY DIMINISH AS THE UPPER ENERGY SHIFTS WELL INTO THE
DAKOTAS.
DRYING TREND IS SHORT-LIVED THOUGH AS STRONGER TROF TRANSITS THE
MT/CANADA BORDER FROM LATE SUNDAY NIGHT THROUGH MONDAY NIGHT.
ENERGY ROTATING AROUND THIS SYSTEM WILL INTERACT WITH RESIDUAL
MOISTURE AND A QUICK RETURN OF EAST-SOUTHEAST LOW LEVEL
WINDS/MOISTURE ADVECTION TO INCREASE PRECIPITATION POTENTIAL FROM
WEST TO EAST OVERNIGHT SUNDAY NIGHT INTO MONDAY MORNING.
PRECIPITATION CHANCES FROM MID MORNING MONDAY THROUGH MONDAY
EVENING WILL BE HIGH (60-90%) ACROSS MUCH OF THE AREA. MODELS HAVE
BEEN TRENDING WETTER WITH THIS SYSTEM AS THEY HAVE INCREASED THE
LOW LEVEL SOUTHEASTERLY WINDS/MOISTURE ADVECTION OVER THE PAST FEW
RUNS. THIS WILL BE THE KEY TO GETTING WIDESPREAD SIGNIFICANT
PRECIPITATION. CURRENT PROBABILITIES FOR MORE THAN A QUARTER INCH
OF PRECIPITATION ON MONDAY ARE 30-40% FOR AREAS EAST OF BILLINGS.
UNSETTLED PATTERN COMES TO AN END TUESDAY WITH A WARMING AND
DRYING PATTERN SETTING UP FOR THE REST OF THE WORK WEEK. DEPENDING
ON THE AMOUNT OF PRECIPITATION THAT FALLS OVER THE NEXT 48 HOURS
OR SO THERE MAY BE ISOLATED LATE DAY WEAK SHOWERS POSSIBLE EACH
DAY, BUT NOTHING IMPACTFUL OR ORGANIZED IS FORECAST DURING THIS
PERIOD. TEMPERATURES CLIMB THROUGH THE WEEK FROM THE LOWER 70S
TUESDAY TO AROUND 90 DEGREES ON FRIDAY.
A SYNOPTIC SCALE PACIFIC LOW PRESSURE SYSTEM IS BEING ADVERTISED
TO IMPACT THE FORECAST AREA FROM FRIDAY NIGHT THROUGH NEXT
WEEKEND. THIS IS STILL A LONG WAYS OUT AND THERE IS A LOT OF
UNCERTAINTY WITH HOW IT MIGHT PLAY OUT. HOWEVER, THIS IS A BIG
SYSTEM THAT COULD BRING IMPACTFUL PRECIPITATION AND THUNDERSTORM
ACTIVITY TO THE AREA NEXT WEEKEND. STAY TUNED THIS WEEK FOR MORE
DETAILS ON THIS SYSTEM ESPECIALLY IF YOU HAVE OUTDOOR ACTIVITIES
PLANNED. CHAMBERS
AVIATION
CLOUDS INCREASE TODAY AS A DISTURBANCE LIFTS INTO THE REGION
BRINGING SCATTERED SHOWERS AND THUNDERSTORMS THIS AFTERNOON INTO
TONIGHT, DEVELOPING OVER THE MOUNTAINS AND MOVING EAST THROUGH THE
AREA. THE MAIN HAZARDS WITH ANY THUNDERSTORM IS HEAVY RAIN
REDUCING VISIBILITY, SUDDEN GUSTY WINDS, AND SMALL HAIL. MVFR TO
IFR CONDITIONS ARE POSSIBLE WITH THE STRONGEST SHOWER/THUNDERSTORM
ACTIVITY. MVFR CEILINGS WILL MOVE IN FROM THE EAST SUNDAY MORNING.
POTENTIAL TS TIMING:
KLVM: 20-03Z
KBIL: 22-04Z
KSHR: 21-05Z
KMLS: 03-09Z
STP/ARCHER
PRELIMINARY POINT TEMP/POPS
SUN MON TUE WED THU FRI SAT
-----------------------------------------------------------
BIL 058/080 054/070 049/076 051/081 055/086 058/091 060/085
52/W 56/T 20/U 00/B 11/B 21/B 24/T
LVM 049/078 046/071 041/077 044/082 047/086 050/088 050/078
51/U 34/T 30/U 01/B 12/T 21/B 36/T
HDN 056/079 053/070 046/075 047/081 051/086 055/091 057/085
53/T 57/T 20/U 00/U 11/U 31/B 24/T
MLS 056/074 052/069 048/071 046/076 050/081 056/086 058/085
55/T 28/T 20/U 00/B 01/U 32/W 23/T
4BQ 055/072 051/070 047/070 046/075 050/080 056/086 059/086
76/T 49/T 40/U 01/U 12/T 41/B 23/T
BHK 051/068 047/069 045/068 042/072 045/076 050/081 054/083
88/T 29/T 41/U 00/B 01/U 23/T 23/T
SHR 051/074 048/067 044/071 043/077 047/081 050/087 053/084
56/T 69/T 51/U 13/T 24/T 32/T 14/T
BYZ WATCHES/WARNINGS/ADVISORIES
MT...NONE.
WY...NONE.
WEATHER.GOV/BILLINGS
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page